Fluid-heating method and apparatus



April 9, 1940. E. e. BAILEY FLUID-HEA'IING METHOD AND AiPARATUS Filed.June 25, 1936 4 Sheets-Sheet 1 INVENT OR.

Ervg'n Bailey ATTORNEY.

' April 9, 1940. E. G.'BAI LE Y 2,196,377

FLUID-HEATING METHOD ANDQPPAIR'AIUS i iled June 2:, 1936 4 Sheets-Sheet2 a 4 INVENTOR.

Ervzn GBai/ey ATTORNEY.

April 9, 1940, Y E. G. BAILEY 2,196,377

FLUID-HEATING METHOD AND APPoKRATUS Filed June 23, 1936 4 Sheets-Sheet 3Fig 3 INVENTOR.

Era/1'17 E. Bailey April 9, 1940. E. s. BAILEY FLUID-HEATING METHOD ANDAPPARATUS Filed June 25, 1936 4 Sheets-Sheet 4 INVENTOR. Era 1'27 G.Bailey B:

0 Y O O O O O O O O O O O O O O OOOOOOOQOOOOOOOOOO ATTORNEY.

Patented Apr. 9, 1940 PATENT cm FLUID-HEATING MEIR-[OD AND APPARATUSErvin G. Bailey, Easton, Pa., 'assignor to The; Babcock & Wilcox ompany,Newai-k, N. J., a corporation of New Jersey Application June 23, 1936,Serial No. 86,737

Y 9 Claims.

My invention relates to methods and apparatus in the art offluid-heating, with particular reference to the superheating of vapors.

An object of the invention is to provide a meth- 0d and apparatus ofthis type, wherebysuperheated vapor is delivered at a substantiallyconstant pressure over an unusually wide range in weight of vapor demandfrom a constant pressure source of supply of saturated vapor.

A further object is to provide a high-capacity superheater whichreceives at least-the major portion of vapor tobe superheated fromindependent generators having their own furnaces, and which is capableof being operated over a wide range of vapor weight demand withoutdamage due to overheating.

A further object is to provide an improved means for equalizingdistribution 'of vapor in a superheater of the type having parallel flowpaths, including the maintenance of uniform pressure conditions at theinlet ends of the several paths, causing the vapor to flow through thepaths at substantially equal velocities and pressure drops, and, withthe arrangement of those paths, to insure that the condition-of thevapor in corresponding portions will be substantially uniform.

A still further object is to provide a radiantly heated superheaterforming a part of'the wall surface of a furnace wherein equal meantemper-.

ature conditions are maintained throughout such wall surface.

These and other objects will'be apparent from an examination of thefollowing description and claims, when taken in connection with theaccompanying drawings, in which:

Fig. 1 is a perspective view illustrating how my invention may beapplied to a superheater of the separately-fired type; 4 Fig. 1A is amodified arrangement of pressure control connections; 7

Fig. 2 is a vertical sectional view illustrating the detail structuralarrangement of the separately-fired superheater of Fig. 1;

Fig. 3 is a horizontal sectional view taken on the line 33 of Fig. 2;

Fig. 4 is a front sectional view for one half of the setting taken onthe line 4-4 of Fig. 2; Fig. 4a is a front elevation (with casingremoved) for the other half of the setting, taken on the line lai4a ofFig. 2;

Fig. 5 is a longitudinal sectional view through the vapor distributorshown in Fig. 1; and

N Fig. 6 is an end view of the distributor with the tube plate brokenaway, as seen from the enlarged outlet end.

Referring now in detail to the construction'illustrated, it will beobserved that I have shown my invention as applied to a separately-firedsu-' 5 perheater, that is to say, a superheater which receives saturatedvapor to be heated, for example, steam from a generator or generatorsfired by means other than the means for firing the superheater and inwhich the pressure of the saturated vapor is controlled. Apparatus ofthis character and of thehigh capacity light construction provided, isespecially useful in connection with power plants for ships wherein attimes during the operation of the ship it is desirable to use saturatedsteam. In such cases the saturated steam may be conducted directly fromthe boiler to the point of use and the furnace of the separatelyfiredsuperheater may be shutdown or operated at a low load which can not beaccomplished in go a case where the superheater is a part of the boilerstructure and heated by gases from the boiler furnace.

It is to be understood at this point, however, that in so far as thebroader aspects of the presg5 ent invention are concerned it is not tobe considered as limited to separately-fired superheaters nor to marineinstallations, for other applications and'uses of the invention will beapparent as the description proceeds.

The separately-fired superheater is indicated generally by the referencecharacter I and comprises a furnace 2 defined by a front wall 3, a rearwall 4, a side wall 5 and a side wall 6. Heat is generated in thefurnace 2 by combustion of u I fuel and the gas passes upwardly througha gas pass I to an outlet 8. The furnace, here shown,

is fired by oil burners 9 and III, the burner 9 being one of largecapacity, and the burners III of small capacity which are arrangedat'each-side of the 40 burner 9 in the manner shown. The purpose ofproviding large and small burners and arranged therein in the mannershown, is to provide a furnace which is highly flexible in operation,yet is capable of attaining unusually high fuel burning 45 rates.

The superheating surface of the separatelyfired superheater l comprisesradiant and convection stages, that is, stages which are mainly heatedrespectively, by exposure to radiant heat of the furnace and by exposureto hot gases of combustion leaving the furnace. Specifically, thesestages include, a radiant section II, a first convection section [2, anda second convection ,section I3. The radiant section I I comprises a BIdefining parallel flow paths for the vapor to be superheated. The tubesIt and I lie closely adjacent or are embedded within and form a part ofthe walls 6, 5 and 6 of the furnace for the purpose of securing themaximum heating surface and in- 7 creasing the capacity of thesuperheater, for protecting the associated walls and for minimizing theduty imposed on the outer casing. The superheater section 52 comprises arow of return bend tubes is extending entirely across the hot gas outletof the furnace 2. For convenience, section 12 has been described as afirst convection section, but due to its location will also be subjectedto radiant heat from the combustion chamber. The second convectionsection l3 comprises rows of return bend tubes l1 and I8 which -20;so asto permit of free expansion from the fixed header. The groups of tubesi1 and it may also ,be suspended from the setting by means of members Mwhich engage lugs22 and 23 secured to outer loops of the respectivegroups permitting tubes to expand from the header ends. Intermediateloops of the groups derive their support from the lug-supported loopsthrough baflie members 2t and 25 which engage the tubes in the severalrows.

An air heater 26 is located above the bank of tubes l8 and consists of aplurality of tubes extending transversely of the gas flue i, ducts 2iand 28-:being provided at opposite ends of the tubes for theaccommodation respectively, of air entering and'leaving the air heater.

As indicated, the tubes of the radiant section ll extend about threesides of the combustion chamber, the side walls 5 and 6 and the rearwall 6,

the tubes id of thebne set being arranged alternately with respect tothe tubes it of the other set. The set'of tubes it has a verticallydisposed outlet header 29 arranged at one side of the front of thefurnace and the other set of tubes has a vertical outlet header 38arranged at the opposite side of the front of the furnace. The inletends of the tubes Hi and it are shown as extending respectively to tubes3| and 32 which are connected to a distributor 33 (see Fig. 1). It willthus be seen that the vapor from the distributor flows through the setsof tubes it and i5 and into the respective headers 29 and 3h. The vaporflows horizontally in one direction left to right through one of thesets of tubes and in the oppodirection right to left through the otherset,

the purpose of which is to provide similar temperature conditionsthroughout the furnace wall structure.

Each of the vertical outlet headers '29 and 3G is connected to ahorizontally-disposed inlet header 3d of the section i2 by means ofsuitable tubes 35 (see Fig. la). The tubes 35 are preferably soproportioned and connected as to provide substantially equal resistancesto the flow of vapor andthus contribute to a substantially uniformdistribution of vapor throughout the several tubes of the sectionsupplied by the'inlet header 3%. The inlet ends of the return-bend.tubes it of the section, it are connected to the header 3:8 andeir-"outlet ends to the inlet header 3% of the plurality of tubes IQ-and I5, arranged in sets and convection section H3. The secondconvection section comprises the inlet header just mentioned, anintermediate header 31, and an outlet header 38. Return bend tubes l1connect the inlet and intermediate headers 36 and 3'! respectively, andreturn bend tubes it connect the intermediate and outlet headers 31 and38 respectively.

Referring to Fig. 1 in the drawings, the saturated vapor is suppliedfrom one or more separate vapor generators (not shown) to vapor mains39, here shown to be two in number. The mains 39 connect into aY-connection 40 and through a pipe 5! and valve 42 to the inlet end. ofthe distributor 33. Pipes 43 connected to outlet header 38 are providedwith valves 44 and terminate in outlet fittings 45.

With the connections described and with valves 42 and it open, all ofthe vapor to be superheated will pass from the mains 39 into thedistributor 33 and from thence through tubes 3| and 32. into thesuperheater tubes, flowing progressively through the several sectionsand finally to the outlets and point or use. Special care must be takenin subdividing the entering vapor in passing from the pipe 4| into theplurality of separate paths through connections 3| and 32,

and into the individual tubes of the radiant section. This isaccomplished by the distributor 33 which is conical in form, expandingfrom the inlet diameter adjacent the valve 42 to a larger and suitablediameter at'its outlet end whereby the velocity of the vapor isequalized over the whole end section. A plate 46 secured to the largeroutlet end, receives the symmetrically arranged distributing connectionswhich conduct vapor to the inlet ends, of the radiantly heated tubes itand iii. The distributor thus equalizes vapor distribution to the inletsof the tubes and, due to its form and the arrangement of connections,efiects the equalization with a minimum loss in velocity head.- Thereis, of course, a drop in pressure due to the vapor passing through theindividual seccreasing loads. In order to protect those portions of thesuperheater which are hottest, that is, sections it and i2 which receiveradiant heat from the furnace, provision is made for maintaining a highenough velocity of vapor through those sections at all times. Theresultant pressure drop therefore, that is safe for that particularportion of the superheater for light loads,

will increase with increase of load so that at maximum load the pressureat the outlet of the radiantly heated section might be reduced beyondpermissible limits. The pressure drop in the-convection portions willalso increase with increasing loads, but not to the same degree as thatin the radiant sections due to the fact that the areas provided for theflow of vapor in the convection sections are larger than the areasprovided in the radiant sections.

tions and, being a function of the rate of vapor fiow, the pressure dropwill be greater for inarea is about the same as the total now area proat pacity of the superheater is considerably limited although thearrangement might be entirely suitable for certain low ranges of vaporflow from minimum to maximum. I therefore provide a more flexible methodin the production of superheated vapor that will not only increase theload range, insure a uniformity in vapor temperature, but will permitthe pressure drop to be maintained within specified limits throughoutthe entire widened load range.

According to the present invention, Iprovide a construction whereinthose portions of the superheater which are subjected to radiant heatare protected by the desired rate of flow of vapor therethrough at allloads and at the same time the capacity of the superheater is notlimited in load range by an excessive pressure drop through theradiantly heated section. I therefore also include a method of operationwhereby the radiantly heated section can be employed to its bestadvantage by suitably controlling the amount of vapor admitted to thatsection and by delivering the remainder of the vapor to be superheateddirectly to a succeeding section of the requisite larger flow area.

For rates above a predetermined vapor flow, part of the vapor issupplied to the inlet header 36 from the mains 39 by means of pipes 41which connect the mains' with a branched fitting 48 leading to the inletheader 36, thus by-passing the radiantly heated portion of thesuperheater. A regulating valve 49' is arranged within the fitting 48and serves to regulate the amount of by-passed vapor added to the header33. The valve 49 may be controlled by any characteristic of the rate ofvapor flow to, through or from the superheater. I have chosen to show apressurecontrolled valve, operating in response to variations in vaporpressure in an outlet pipe 43 leading from the outlet header of thesuperheater. The pipe 50 connects the outlet pipe 43 with a suitablevalve-actuating device 5| which automatically operates the valve 49 in amanner well known in the art. For a given pressure in the mains 39, thepressure in the outlet pipe 43 is indicative of the pressure dropthrough the entire superheater, and with the pressure at the inlet endmaintained substantially constant, any va'riations in pressure at theoutlet will provide impulses for the valve 49 which are directly relatedto the pressure drop across the entire superheater. Similarly,controlling the valve by'a pressure at some intermediate point in'thepath of vapor flow would provide an actuating impulse which is alsodirectly related to the pressure drop up to the selected intermediatelocation. a

For certain conditions, it might be preferred to have the valve 49actuated directly in response to the difference in pressure between twoselected points in the path of vapor flow, irrespective of the pressureof the vapor supplied to the superheater, in which case the valve 49would be controlled by pressures from the'two selected points.

- Fig, 1A is representative of the arrangement thus modified wherein thevalve-actuating device I51, of a known type operable in response topressure difierentials, is connected by pipes I52 and I53 respectivelyto points in the path of vapor flow of relatively high and lowpressures; pipe 52 be-- ing connected to the header 36. by meansincluding the elbow fitting I54 and therefore subject to pressure ofvapor at the outlet end of the section comprising radiantly heated tubesl6; pipe I53 being connected to valve I42 at the en+ trance todistributor 33 and therefore subject to pressure of vapor beingdelivered to the superheater unit.

In the specific embodiments shown, when the rate of vapor flow throughthe superheater is such that the pressure drop over a given portion isunduly increased and the pressure of'the vapor leaving the superheateris correspondingly reduced, the regulating valve 49 is automaticallyoperated to by-pass vapor around the radiantly heated section to theinlet header of the convection section. In this manner, a predeterminedamount of vapor passes through one portion of the superheater sufliclentto protect it against overheating, and within the permissible pressuredrop for that portion, and any additional vapor to be superheatedby-passes that portion and flows through the succeeding section in whichthe flow path is of larger cross-sectional area. The

larger area compensates for the greater rate of flow with the resultthat the over-all pressure drop is less than would be the case if thetotalamount of vapor caused to pass in series through all sections ofthe superheater. The pressure of the vapor in the pipes 41 is, ofcourse, the same as the pressure of the vapor supplied to thedistributor 33 but the valve 49' acts to reduce the pressure of vaporflowing direct to the convection portion below that of the vapor flowingto the radiantly heated section. Consequently, there is no interferencewith the flow of vapor to the radiantly heated section, and yet thepressure is not reduced to an amount which would prevent the flow ofby-passed vapor into the inlet header 36. The valve 49 is opened anamount suflicient to provide vapor flow from the pipes 41 into theconvection section but not to such an amount which would build up a highbackpressure that might prevent or seriously reduce the flow of vaporthrough the radiantly heated section.

When the control valve 49 is brought into operation due to thepredetermined pressure differential across the entire unit as in Fig. 1,or across the elementary form shown might have certain characteristicsof operation which would cause a temporary fluctuation in pressure andvapor flow conditions at the header 36 when changing from one load toanother; however, such conditions will soon subside since the basicoperation of the valve is unaffected, and the valve being continuouslysubject to the pressure values for which it is set will open and closethe bypass connection as required in response to such pressure values.

In conjunction with the distribution of vapor to the various sections ofthe superheater at difierent loads, I also provide for a regulation ofcombustion conditions, so that heat is supplied to the superheater in aneffective manner, and in coordination with the load. A desirable methodis to operate only the larger andcentrally located burner 9 for thelower rates of vapor flow through the superheater, and as the load isincreased, cut

in one or more of the smaller burners Ill in orderto maintain a requiredexit temperature of the vapor. The changeover from one to a plurality ofburners is made at approximately the time when the regulating valve 69is opened, and under a load condition which insures a suitable quantityof well distributed vapor passing through and protecting the radiantlyheated tubes. Burner e may appropriately be automatically controlled inresponse to the temperature of the superheated vapor. The controls forburners d and H), as in= dicated in Fig. l, comprise control devices iiiand N2 of known types, arranged for controlling the supply of fuelthrough pipes Hi9 and lid respectively; device ill, for burner 9, beingconnected by pipe M3 to a thermally responsive element M5 at the outletof the superheater, and device 2 i2, for one or more burners Hi, beingconnected by pipe lid and fitting M6 to control pipe 5% through whichvariations in vapor pressure are transmitted. 7

An additional feature of my invention consists in connecting thebranched-fitting 38 with the outlets 515, by means of pipes 52 andvalves 53. These additional connections are, in eiiect, continuations ofthe pipes di, '50 that saturated vapor may be shunted entirely, or inpart, around the superheater depending on the conditions orcircumstances which would make such an arrangement desirable. Byproviding separate pipe connections d? from each of the mains 39, andalso separate pipe connections :13 and 52 leading to the outlet fittings65, a greater flexibility in operation may be had. In addition to beingable to by-pass the superheater as already described, it is possible todeliver saturated and superheated steam in separate streams, independentof the number of generators supplying steam to the mains.

I claim:

1. The method of I superheating a variable quantity of vapor to apredetermined temperature and at pressures within given limits,whichcomprises delivering heat to said vapor from a source separate irom thatrequired for vaporgeneration, causing a part of the vapor to flowthrough tubes exposed to radiant heat from said separate source,maintaining the pressure of vapor supplied to said radiantly heatedtubes substantially constant causing additional vapor to be combinedwith the radiantly heated part for fiow therewith through tubes heatedby convection, regulatingthe quantity of vapor so combined in accordancewith a factor determined by the total quantity of vapor delivered to thesuperheater, and increasing the amount of heat deiivered in accordancewith the admission of the additional vapor to the second section.

2. Furnace apparatus comprising, in combination, means providing acombustion chamber, means providing for the combustion of fuel in saidchamber, a superheater comprising a radiantly heated superheater sectionand a convection-heated superheater section, means providaaoaevv ing forthe flow of vapor serially through the radiantly heated section and. theconvectionheated section, means for maintaining the pressure of vaporsupplied to said superheater substantially constant, and means forbypassing the radiantly heated section and at increased loads supplyingadditional vapor direct to the convection-heated section when thepressure drop across the superheater reaches a predetermined value. I

3. The combination with a furnace including wall means defining acombustion chamber and means for burning fuel in said chamber, of aradiantly heated superheater comprising a row of substantially paralleltubes in heat transfer relation to the wall means which define thecombustion chamber and being divided into two sets with the tubes of oneset arranged alternately with respect to the tubes of the other set, andmeans providing for the fiow of separate quantities of vapor to besuperheated through the sets in opposite directions including means foradmitting vapor of substantially equal amounts and temperatures to therespective sets so as to produce a substantially uniformtemperat'urecondition throughout the associated wall means.

4. The combination with a furnace including wal means, defining acombustion chamber and means for burning fuel in said chamber, of aradiantly heated superheater comprising a row of substantiallyhorizontal and parallel tubes arranged in heat transfer relation to andcoextensive with the greater portion of the wall means defining thecombustion chamber, the row of tubes being divided into two sets withthe tubes of one set arranged alternately with respect to the tubes ofthe other set, and means providing for the flow of separate quantitiesof vapor to be superheated through one of the sets in one direction andthrough the other set in the opposite direction including means foradmitting vapor of substantially equal amounts and temperatures to therespective sets so as to produce a substantially uniform temperaturecondition throughout said greater portion of the wall means.

5.The method of superheating vapor under pressure at different loadswhich comprises passing said vapor at low loads successively throughdifferent heating zones having difierent resist ances to vapor flow forcorresponding loads, and at higher loads passing the additional vaporthrough a zone of lower resistance in combination with vapor heated in azone of higher resist ance, and maintaining the amount of vapor passedthrough said zone of higher resistance substantially constant at saidhigher loads in accordance with a predetermined pressure drop across atleast one of said zones.

- j 6. The method of superheating vapor under pressure throughout agiven load range and within predetermined limits of pressure drop acrossseparated points in the patch of vapor fiow which comprises passing saidvapor at low loads successively through different heating zones, in

one of which zones the vapor is heated mainly by radiation and inanother of which the vapor is heated mainly by convection, and at higherloads by-passing said radiant zone and causing the additional amounts ofvapor to flow only through said convection zone in combination withvapor from said radiant zone while maintaining the amount of vaporflowing through the radiant zone substantially constant, and controllingthe relative amounts of vapor flowing through said zones for loadswithin said. given range in accordance with a predetermined pressuredrop across separated points in the path of vapor flow.

7. The method of superheating vapor under pressure at difierent loadswhich comprises passing said vapor through different heating zones, inone of which zones the vapor is heated mainly by radiant heat fromburning fuel at a relatively high pressure drop for a given load and inanother of which the vapor is heated mainly by convection from gases ofcombustion from said fuel at a relatively low pressure drop for the sameload, passing vapor at one load successively through said zones of highand low resistance and at an increased load passing the additional vaporthrough a zone of low resistance in combination with vapor heatedin azone of high resistance, and controlling the admission of saidadditional vapor to said zone of low resistance in accordance withpressure drop across separated points in the path of vapor flow whilemaintaining the amount of vapor flowing through said zone of highresistance substantially constant.

8. The method of superheatlng vapor under pressure at different loadswhich comprises heating regulated quantities of said vapor in differentheating zones, including passing a quantity of vapor successivelythrough all or said zones and at the higher loads bypassing the vapor inexcess of said successively heated quantity through less than the totalnumber 01 zones, and regulatin heat input to at least one of said zonesin synchronism with the bypassing of said excess vapor whereby heatinput at said higher loads is increased and decreased substantially inaccordance with load variations;

9. In combination with a furnace havin means for the combustion of fueltherein at varying rates of heat input to said furnace, a superheaterhaving sections of tubes in series, one section comprising tubes exposedto radiant heat from said combustion means and another comprising tubesheated mainly by convection by gases of combustion from said furnace,means for suppiying vapor to be superheated to said tubes, one partbeing admitted to said radiantly heated section and being caused to flowthrough both of said sections in series, another part of said vaporbeing admitted intermediately of said sections and being caused to flowthrough said convection-heated section in combination with vapor fromsaid radiantly heated section, means for controlling the relativeamounts of vapor flowing through said sections, and means forcontrolling the heat input to said furnace in accordance with saidrelative vapor flow.

1 KEVIN G. BAILEY.

,pmi 001mm,, line 55, after -"ve.p'o1 insert "were",

- CERTIFICATE OF CORRE TION.

Patent- No 2,196,577. A ril 9,. 19m.

" ERVIN G. BAILEY.

It; is hereby 'c ertiiii eid. that .erroz h'ppeafs in the printedspecification 0f the above numbered patent requiringfcorrec tion asfollows: Page 5, secpagei h, second. column,

63, claim 6, for the word patch read.,--'pat b,--; that the said.

lhettgefe Petent shouid be pead with this correction therein tht the ewemay confdn'g to .therecord of the case "in the Patent Office.

.S1gned and sealed this 9121- day of July, A. n.19ho.'

Henry Van Arsdale (Seal) Acting Commissioner "of Patents.

